This invention relates to an airflow velocity vane actuated switch, and more particularly to such an airflow velocity switch for use in sensing cooling fluid flow in cooling systems.
In applications where cooling is required for equipment subject to thermal destruction, thermostats have often been used at the location of the equipment to be cooled. Thermostats may sense the temperature of the cooled equipment, but often only provide an indication after the destructive temperature has been reached. A cooling system using thermostatic sensors will not provide early detection of failure of the prime mover of the coolant fluid. If a fan, for example, in an air cooling system becomes inoperable, early warning of the failure would prevent destruction of the temperature sensitive equipment.
A device for sensing when a cooling fan motor is inoperable also provides only limited protection against thermal destruction. There are generally air filters upstream from the fan for cleansing the cooling airflow. The filters may become clogged by contaminants removed from the airflow, thus blocking cooling airflow from the equipment to be cooled.
A need therefore exists for means to sense the flow of the cooling fluid so that the temperature sensitive equipment may be shut down prior to thermal destruction in the event such flow stops. Prior art means for sensing coolant flow has utilized microswitches actuated by lever arms having attached vanes of varying area for disposition in the fluid flow. Larger vane areas were required for lower coolant flow velocities, and smaller vane areas were acceptable for higher coolant velocities. The prior art vane switches therefore require a multiplicity of vanes having considerable dimensions for monitoring a multiplicity of coolant velocities. There is therefore a need for a device which will monitor coolant velocities near the source for coolant motion, and which may be adjusted readily to monitor a variety of such velocities without altering the dimensions of the vane in the airflow.